Nano-thick cobalt-iron spinel oxides (cobalt ferrites) have been synthesized via atomic layer deposition (ALD) on yttria-stabilized zirconia (YSZ) and Al₂O₃ nanoparticles. Multilayers of cobalt(II) oxide and iron(II,III) oxide were deposited and subsequently heat treated at 900 ^oC. X-ray diffractometry (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to determine film crystallinity and oxidation state, and induced coupled plasma - atomic emission spectroscopy (ICP-AES) was verified the relative amounts of cobalt and iron.

ALD of ferrites has the advantage of being able to precisely control the thickness and Co/Fe ratio on the atomic level, which is significant because it has been suggested in the literature that this two-step cycle water splitting cycle is a surface dominated reaction. The kinetics of the water splitting step has been investigated and results indicate that the temperature required is decreased due to a reduction of diffusion limitations. Additionally, results were directly compared to samples synthesized via traditional methods (coprecipitation, etc), and the amount of hydrogen generated per mole of ferrite was shown to be greater. Potential factors affecting the water splitting step that were studied included film thickness, Co/Fe ratio, and the substrate material (YSZ and Al₂O₃), and each was shown to be statistically significant. Hydrogen evolution was measured in situ using a residual gas analyzer, and changes in crystallinity were measured using a powder x-ray diffractometer.